The present invention relates to an improved rod locking device having particular application to locking the tail rod of a blowout preventer ram in position to prevent movement of the ram once it has been closed.
When oilfield ram type blowout preventers are in use, it occasionally becomes necessary to lock the rams in the closed position. The prior art of blowout preventers has numerous devices for locking a ram in its closed position. Such devices range from a simple mechanical screw which is threaded through the bonnet to engage the outer end of the ram tail rod or piston to prevent its movement in the outward direction to complicated devices such as shown in U.S. Pat. No. 4,305,565 wherein a locking cone responds to fluid pressure during the movement of the ram to move the locking wedges into engagement with the tapered inner surfaces of the housing.
Prior to the present invention rod locking devices have included wedges actuated by pistons which are actuated when the rod is in its position for locking and the wedges are moved into locking engagement with a tapered surface on the rod to prevent retraction of the rod from its locked position. A typical example of this type of device is disclosed in U.S. Pat. No. 3,208,357, issued Sept. 28, 1965 to H. Allen et al.
Other prior art patents, such as U.S. Pat. Nos. 4,052,995, 4,076,208 and 4,290,577 disclose ram locks wherein a lock nut is stopped from rotating by a clutch mechanism which has ratchet teeth.